What size of softbox can be used on a 430 EXII?

I would like to get a softbox for my 430 EXII, but I am not sure what size to get. What size works good for family portraits, waist up portraits, or headshots. What is the biggest size possible that will work on the 430 EXII.

Re: What size of softbox can be used on a 430 EXII?

As kvbarkley points out - it really does depend on the subject distance. Most of the soft-boxes designed for shoe-mount flashses are in the 24-30" size range. Bigger soft-boxes are designed more with studio lights in mind. It occurs to me that I have seen larger systems but I think they were designed to mount multiple flashes to fire into the same softbox.

While bigger generally is more desirable, anything that broadens the light from a pin-point source to something wider will help take the hard edge off the transitions from shadow to hightlights.

I typically flip out the wide-diffuser panel (the thing that slides out and hinges down in front of the flash) when using the flash in a soft-box to keep it from firing a concentrated area of light into the fabric on the front of the box (I want the light to scatter as wide as possible.)

I have used a smaller softbox before, but I think bigger is better to get more soft shadows. I use three or four speedlites outside in daylight. Inside in a darker room I can use one speedlite in my softbox/octabox.

Re: What size of softbox can be used on a 430 EXII?

I actually have Sly's book. Its Probably my favorite Photography book. However, The section on softboxes is rather short. He does mention using a softbox with multiple flashes inside for larger softboxes. I want to avoide that because I am using Canon's Wireless feature and that would block the line of sight.

I am looking for a softbox with a speedring that I can mount the flash on the back so I can still use the wireless feature. The softbox I am looking at is by Fotodiox. It is octagon shaped and up to 70" but I might go smaller. Is there much a difference between the rectangular or octagon shaped softboxes? And is there much of a difference between the shoot through softboxes vs. one with a silver interior with the flash mounted inside?

I normally use two ~ 30" shoot through umbrellas for portraits, but now I am looking to do more black and white portraits and want some light that is a little stronger, but not as harsh as the direct flash.